A method for controlling MRAM magnetic tunnel sidewall contamination

Abstract

The application provides a method for controlling MRAM magnetic tunnel wall contamination, which does not need to additionally plate an insulating protective layer on the MTJ layer wall, but forms a unique funnel-shaped groove in the etching process, the funnel-shaped groove comprises a first region away from the plane of the substrate and a second region adjacent to the plane of the substrate, the size of the first region gradually increases in the first direction, and the size of the second region is constant in the first direction; when removing the metal contamination at the bottom of the funnel-shaped groove, the funnel-shaped groove can prevent the metal contamination from adhering to the wall of the MTJ layer, thereby improving the device performance of the MRAM.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip manufacturing technology, and more specifically, to a method for controlling contamination on the sidewalls of MRAM magnetic tunnels. Background Technology

[0002] With the continuous development of science and technology, various types of memory have been widely used in people's lives and work, bringing great convenience to people's lives.

[0003] In the random access memory (RAM) market, magnetic random access memory (MRAM) is a relatively new type of RAM. Compared to traditional dynamic random access memory (DRAM), static random access memory (SRAM), and flash memory, MRAM has higher read and write speeds than flash memory, as well as radiation resistance and non-volatility, which SRAM and DRAM do not possess. Therefore, many storage requirements that currently require a combination of these three types of memory can often be met by MRAM alone.

[0004] However, during the current manufacturing process of MRAM magnetic tunnels, a layer of metal contamination forms on the sidewalls of the magnetic tunnels, which can lead to the failure of MRAM devices. Summary of the Invention

[0005] In view of this, to solve the above problems, the present invention provides a method for controlling contamination of the sidewall of an MRAM magnetic tunnel, the technical solution of which is as follows:

[0006] A method for controlling contamination of the sidewall of an MRAM magnetic tunnel, the method comprising:

[0007] A basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode;

[0008] The first etching process is performed on the surface of the upper electrode facing away from the substrate until the substrate is exposed, and the size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction.

[0009] The second etching process is continued to make the dimensions of all regions of the lower electrode equal in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the dimensions of the first region gradually increase in the first direction, and the dimensions of the second region remain unchanged in the first direction;

[0010] Remove metal contaminants from the bottom of the funnel-shaped groove.

[0011] Preferably, in the above control method, the distance between the surface of the MTJ layer facing away from the upper electrode and the surface of the first region facing away from the second region is Hs;

[0012] The thickness of the lower electrode in the first direction is G1;

[0013] Where Hs > G1, or Hs = G1.

[0014] Preferably, in the above control method, the first etching process includes:

[0015] The upper electrode is first etched from the surface away from the substrate using plasma beam etching until the substrate is exposed. The size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction.

[0016] Preferably, in the above control method, the ion energy in the plasma beam etching method is 50V-600V;

[0017] Ion acceleration bias voltage is 50V-1000V;

[0018] The gas flow rate is 10 sccm-500 sccm.

[0019] Preferably, in the above control method, the gas in the plasma beam etching mode is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

[0020] Preferably, in the above control method, before performing the first etching process, the control method further includes:

[0021] A mask layer is provided on the surface of the upper electrode facing away from the substrate, and the mask layer includes a plurality of mask units.

[0022] Preferably, in the above control method, the distance between two adjacent mask units is X; the thickness of each mask unit in the first direction is Y3; and the total thickness of the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y2.

[0023] The total thickness of the mask unit, the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y1, where Y1 = Y2 + Y3;

[0024] Define the first angle Second angle The third angle is A3, where 0 < A3 - A2 ≤ 5°;

[0025] In the plasma beam etching method described above

[0026] The incident angle of the ion beam is greater than A1 and less than A3.

[0027] Preferably, in the above control method, the second etching process includes:

[0028] A second etching process is performed using reactive ion etching to ensure that at least all regions of the lower electrode have equal dimensions in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the first region gradually increases in size in the first direction, and the second region remains unchanged in size in the first direction.

[0029] Preferably, in the above control method, the DC bias voltage in the reactive ion etching method is less than or equal to the ion energy in the plasma beam etching method.

[0030] Preferably, in the above control method, the selectivity ratio of etching medium to etching metal in the reactive ion etching mode is greater than 1.5.

[0031] Preferably, in the above control method, the etching thickness of the substrate in the reactive ion etching method is greater than 10 nm.

[0032] Preferably, in the above control method, the source electrode power in the reactive ion etching method is 100W-1000W;

[0033] The bias electrode power is 100W-1500W;

[0034] The etching chamber pressure is 2mT-20mT;

[0035] The gas flow rate is 10 sccm-500 sccm.

[0036] Preferably, in the above control method, the gas in the reactive ion etching mode is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

[0037] A method for controlling contamination of the sidewall of an MRAM magnetic tunnel, the method comprising:

[0038] A basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode;

[0039] The first etching process is performed on the surface of the upper electrode facing away from the substrate until the lower electrode is exposed. The size of a portion of the MTJ layer adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the MTJ layer remains unchanged in the first direction.

[0040] The second etching process is continued to make the size of all regions of the MTJ layer equal in the first direction, and the substrate and the lower electrode have funnel-shaped trenches, wherein the funnel-shaped trenches include a first region of the lower electrode and a second region of the substrate, the size of the first region gradually increases in the first direction, and the size of the second region remains unchanged in the first direction;

[0041] Remove metal contaminants from the bottom of the funnel-shaped groove.

[0042] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0043] This invention provides a method for controlling sidewall contamination in MRAM magnetic tunnels. Instead of depositing an additional insulating protective layer on the MTJ layer sidewalls, a unique funnel-shaped trench is formed during the etching process. This funnel-shaped trench includes a first region facing away from the substrate bottom surface and a second region adjacent to the substrate bottom surface. The size of the first region gradually increases in the first direction, while the size of the second region remains constant in the first direction. When removing metal contamination from the bottom of the funnel-shaped trench, this trench can prevent metal contamination from adhering to the sidewalls of the MTJ layer, thereby improving the device performance of the MRAM. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 A simplified schematic diagram of a single byte of MRAM;

[0046] Figure 2 This is a schematic diagram illustrating the working principle of MTJ;

[0047] Figure 3 A simplified diagram of a single byte structure for another type of MRAM;

[0048] Figure 4 This is a schematic diagram of an MRAM cleaning method for cleaning metal contaminants in trenches;

[0049] Figure 5 This is a schematic diagram of metal contamination after MRAM cleaning of a trench.

[0050] Figure 6 This is a schematic diagram illustrating the performance of an MRAM with metal contamination.

[0051] Figure 7 A flowchart illustrating a method for controlling contamination of the sidewall of an MRAM magnetic tunnel, provided in an embodiment of the present invention;

[0052] Figures 8-12 for Figure 7 A schematic diagram of the control method shown;

[0053] Figure 13 This is a schematic diagram of the structure corresponding to the completed MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention;

[0054] Figure 14 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0055] Figure 15 A flowchart illustrating another method for controlling contamination of the sidewall of a magnetic tunnel provided in an embodiment of the present invention;

[0056] Figure 16 A schematic diagram of a structure before the start of a method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0057] Figure 17 This is another structural schematic diagram corresponding to the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in this embodiment of the invention before it begins;

[0058] Figure 18 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0059] Figure 19 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0060] Figure 20 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0061] Figure 21 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0062] Figure 22 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0063] Figure 23 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention;

[0064] Figure 24 This is a schematic diagram of a structure corresponding to the completion of another method for controlling contamination of the sidewall of a magnetic tunnel provided in an embodiment of the present invention. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Based on the content recorded in the background art, refer to Figure 1 , Figure 1 This is a simplified schematic diagram of a single byte of MRAM; as shown. Figure 1 As shown, the entire MRAM structure sits on a substrate, with a lower electrode, a magnetic tunneling junction (MTJ), and a top electrode sequentially arranged in a certain direction; among them, the MTJ is a key structure of the MRAM device, as shown... Figure 1 As shown, in this direction, the MTJ includes: a fixed magnetic layer, an insulating layer, and a free magnetic layer.

[0067] It should be noted that this direction is perpendicular to the substrate and points from the substrate toward the lower electrode.

[0068] based on Figure 1 The MRAM structure shown is referenced. Figure 2 , Figure 2 This is a schematic diagram illustrating the working principle of MTJ; for example... Figure 2 As shown, when current is passed through the MTJ layer, the current can tunnel through because the insulation layer is very thin (usually a few nanometers); the magnetic pole direction of the fixed magnetic layer is fixed, while the magnetic pole direction of the free magnetic layer can be changed.

[0069] When the magnetic poles of the fixed magnetic layer and the free magnetic layer are aligned (parallel), the MTJ exhibits a smaller resistance (Rp) and a larger tunneling current (Ip). This means the entire structure can be considered to be in a conducting state, representing a "1" in a binary byte.

[0070] When the magnetic poles of the fixed magnetic layer and the free magnetic layer are opposite (anti-parallel), the MTJ exhibits a larger resistance (Rap) and a smaller tunneling current (Iap). This means the entire structure can be considered to be in a non-conductive state, representing a binary byte "0".

[0071] Therefore, the performance of MTJ is measured by tunneling magnetoresistance (TMR), and the formula for TMR can be written as:

[0072]

[0073] The larger the TMR, the better the MRAM performance.

[0074] As can be seen from the above formula, the inventors discovered that the smaller the on-state resistance (Rp) and the larger the off-state resistance (Rap), the greater the difference between the on-state current (Ip) and the off-state current (Iap), and the better the device performance.

[0075] refer to Figure 3 , Figure 3 This is a simplified diagram of a single byte structure for another type of MRAM. Figure 1 Multiple MRAM single-byte structures, as shown, can be arranged into an array and interconnected with wires to form a... Figure 3 The diagram shows a simple MRAM storage structure.

[0076] like Figure 3 As shown, multiple MRAM single-byte structures form a trench morphology, which can also be understood as the magnetic tunnel structure of MRAM.

[0077] Typically, MRAM manufacturing processes utilize plasma beam etching or reactive ion etching. Since the primary component of an MRAM structure is metal, non-volatile etching byproducts—metal contaminants—are generated during etching. Some of these metal contaminants inevitably fall into the trench, forming a layer of contaminants within the trench.

[0078] A cleaning step is required after etching to remove metal contaminants from the grooves.

[0079] refer to Figure 4 , Figure 4 This is a schematic diagram of an MRAM cleaning process for metal contamination in a trench. The cleaning step is generally a low-energy etching step that bombards the bottom of the trench, causing the metal contamination to be sputtered away from the trench.

[0080] refer to Figure 5 , Figure 5 This is a schematic diagram of metal contamination after cleaning an MRAM trench. Following the cleaning steps, as shown... Figure 5 As shown, some metal contamination adheres to the MRAM structure, especially on the sidewalls of the MTJ.

[0081] refer to Figure 6 , Figure 6 This is a schematic diagram illustrating the performance of an MRAM with metal contamination, such as... Figure 6 As shown, when there is metal contamination on the sidewall of the MTJ layer, when current is passed through the MTJ layer, the current does not need to tunnel through the insulating layer, but can flow directly through the metal contamination on the sidewall, forming a conducting current (I). Therefore, regardless of whether the magnetic poles of the fixed magnetic layer and the free magnetic layer are aligned, the conducting current is unaffected, that is, Ip = Iap = I. In this case, TMR = 0, indicating that the MRAM device has failed.

[0082] Based on this, one solution in the prior art is to plate an insulating protective layer on the sidewall of the MTJ layer to prevent the MTJ from conducting due to metal contamination on the sidewall.

[0083] However, the inventors discovered that because the MRAM manufacturing process requires switching between different devices, the current production capacity of this solution is very limited, and the critical dimension (CD) of MRAM is also difficult to control.

[0084] Based on this, the present invention provides a method for controlling contamination on the sidewall of an MRAM magnetic tunnel, which can greatly clean the metal contamination inside the MRAM magnetic tunnel without affecting the device performance of the MRAM.

[0085] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0086] refer to Figure 7 , Figure 7 This is a flowchart illustrating a method for controlling contamination of the sidewall of an MRAM magnetic tunnel, as provided in an embodiment of the present invention.

[0087] The control method includes:

[0088] S101: As Figure 8 As shown, a basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode.

[0089] S102: As Figure 9 As shown, the first etching process is performed on the surface of the upper electrode away from the substrate until the substrate is exposed, and the size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction.

[0090] In this step, the size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction; the size of the remaining portion of the lower electrode remains unchanged in the first direction, thus forming... Figure 9 The "tail" structure shown.

[0091] S103: As Figure 10 As shown, a second etching process is performed to make at least all areas of the lower electrode equal in size in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the size of the first region gradually increases in the first direction, and the size of the second region remains unchanged in the first direction.

[0092] In this step, the "tail" structure formed in step S102 will act as a mask in step S103. Under the effect of this mask, after the second etching is completed, a funnel-shaped groove will be formed, namely a funnel-shaped groove.

[0093] S104: As Figure 11 As shown, remove metal contaminants from the bottom of the funnel-shaped groove.

[0094] In this embodiment, the method for controlling sidewall contamination of the MRAM magnetic tunnel does not require an additional insulating protective layer to be deposited on the MTJ layer sidewall. Instead, it forms a unique funnel-shaped trench during the etching process. This funnel-shaped trench includes a first region facing away from the substrate bottom surface and a second region adjacent to the substrate bottom surface. The size of the first region gradually increases in the first direction, while the size of the second region remains constant in the first direction. Figure 11 and Figure 12 As shown, when removing metal contaminants from the bottom of the funnel-shaped trench, some of the sputtering paths of the contaminants are blocked by the protruding position at the junction of the first and second regions in the funnel-shaped trench. Most of the metal contaminants will only adhere to the sidewall of the upper electrode and not to the sidewall of the MTJ layer. Therefore, no pathway will be formed on the sidewall of the MTJ layer, thereby improving the device performance of the MRAM.

[0095] Optionally, in another embodiment of the invention, reference is made to... Figure 13 , Figure 13 This is a schematic diagram of the structure corresponding to the completed MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention; see reference. Figure 14 , Figure 14 This is another structural schematic diagram corresponding to the completion of a method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention.

[0096] The distance between the surface of the MTJ layer facing away from the upper electrode and the surface of the first region facing away from the second region is Hs;

[0097] The thickness of the lower electrode in the first direction is G1;

[0098] Where Hs > G1, or Hs = G1.

[0099] In this embodiment, the difference in effect between the size relationship between Hs and G1 lies in the blocking effect on the metal contamination sputtering path. In comparison, the morphology with Hs = G1 has a better blocking effect on the metal contamination sputtering path than the morphology with Hs > G1.

[0100] like Figure 14 As shown, when Hs > G1, that is, in the second etching process, the entire area of ​​the lower electrode is made to have the same size in the first direction, and a portion of the substrate of the adjacent lower electrode is also made to have the same size in the first direction. Other areas of the substrate have funnel-shaped trenches, wherein the funnel-shaped trenches include a first area away from the bottom surface of the substrate and a second area adjacent to the bottom surface of the substrate. The size of the first area gradually increases in the first direction, while the size of the second area remains unchanged in the first direction.

[0101] Optionally, in another embodiment of the invention, reference is made to... Figure 15 , Figure 15 A flowchart illustrating another method for controlling contamination of the sidewall of a magnetic tunnel provided in an embodiment of the present invention.

[0102] Before the first etching process, the control method further includes:

[0103] S105: As Figure 8 As shown, a mask layer is disposed on the surface of the upper electrode facing away from the substrate, and the mask layer includes multiple mask units.

[0104] In this embodiment, a mask layer is provided on the surface of the upper electrode away from the MTJ layer above the basic structure. Depending on the situation, the material of the mask can be TiN, Ta, C, Si, SiO, SiN or different combinations of the above materials, which is not limited in this embodiment of the invention.

[0105] Optionally, in this embodiment of the invention, the first etching process includes:

[0106] The upper electrode is first etched from the surface away from the substrate using plasma beam etching until the substrate is exposed. The size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction.

[0107] In other words, the etching method for the first etching process is Ion Beam Etching (IBE), specifically:

[0108] In the plasma beam etching method, the ion energy is 50V-600V.

[0109] The ion acceleration bias voltage is 50V-1000V.

[0110] The gas flow rate is 10 sccm-500 sccm.

[0111] In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

[0112] It should be noted that the etching amount of the first etching process needs to be determined according to the actual situation, but it is necessary to ensure that the etching stops at the interface between the lower electrode and the substrate.

[0113] like Figure 9As shown, based on the masking effect of IBE etching, a "tail" structure will be formed in the lower electrode region after the first etching is completed.

[0114] refer to Figure 16 , Figure 16 This is a schematic diagram of a structure corresponding to the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention.

[0115] The distance between two adjacent mask units is X; the thickness of each mask unit in the first direction is Y3; the total thickness of the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y2;

[0116] The total thickness of the mask unit, the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y1, where Y1 = Y2 + Y3;

[0117] Define the first angle Second angle The third angle is A3, where 0 < A3 - A2 ≤ 5°;

[0118] In the plasma beam etching method described above

[0119] The incident angle of the ion beam is greater than A1 and less than A3.

[0120] It should be noted that the reference Figure 17 , Figure 17 This is another structural schematic diagram corresponding to the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in this embodiment of the invention. The ion beam incident angle is the angle between the ion beam incident direction and the normal, or the angle between the ion beam incident direction and the first direction.

[0121] It should be noted that while large-angle IBE etching can effectively prevent metal contamination on the sidewalls of the MTJ layer, excessively large IBE angles can lead to undersized critical dimensions and performance degradation. Conversely, excessively small IBE angles prevent the formation of funnel-shaped trenches, resulting in metal contamination on the sidewalls of the MTJ layer. Therefore, in this embodiment of the invention, the ion beam incident angle is set to be greater than A1 and less than A3 to ensure the performance of the MRAM device while minimizing metal contamination on the sidewalls of the MTJ layer.

[0122] Optionally, in this embodiment of the invention, the second etching process includes:

[0123] A second etching process is performed using reactive ion etching to ensure that at least all regions of the lower electrode have equal dimensions in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the first region gradually increases in size in the first direction, and the second region remains unchanged in size in the first direction.

[0124] In other words, the second etching process uses reactive ion etching (RIE), specifically:

[0125] The DC bias voltage in the reactive ion etching method is less than or equal to the ion energy in the plasma beam etching method.

[0126] In the reactive ion etching method, the selectivity ratio of etching medium to etching metal is greater than 1.5.

[0127] In the reactive ion etching method, the etching thickness of the substrate is greater than 10 nm.

[0128] In the reactive ion etching method, the source electrode power is 100W-1000W;

[0129] The bias electrode power is 100W-1500W;

[0130] The etching chamber pressure is 2mT-20mT;

[0131] The gas flow rate is 10 sccm-500 sccm.

[0132] In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

[0133] like Figure 10 As shown, the "tail" structure formed during IBE etching acts as a mask during RIE etching. Under this masking effect, a funnel-shaped trench morphology is formed after RIE etching is completed, i.e., funnel-shaped trench.

[0134] It should be noted that the low loading effect in RIE etching can, to some extent, compensate for the loading effect brought about by IBE etching.

[0135] Furthermore, during the invention process of this invention, the inventors discovered that increasing the amount of etching on the substrate during RIE etching increases the ability to clean metal contamination at the bottom of the funnel-shaped trench, makes the protruding structure at the junction of the first and second regions of the funnel-shaped trench less obvious, and increases the degree of metal contamination on the sidewalls of the MTJ layer.

[0136] Furthermore, insufficient RIE steps will lead to excessive metal contamination at the bottom of the funnel-shaped trench, causing the two MRAM bytes to conduct to each other; excessive RIE steps will lead to excessive metal contamination on the sidewalls of the MTJ layer, causing a single MRAM byte to fail. Based on this, some RIE etching parameters described in the above embodiments are limited.

[0137] Optionally, in another embodiment of the invention, reference is made to... Figure 18 , Figure 18 This is another structural schematic diagram corresponding to the completion of the method for controlling contamination of the sidewall of an MRAM magnetic tunnel provided in an embodiment of the present invention.

[0138] like Figure 18 As shown, the width of the bottom of the funnel-shaped groove is defined as L2, the width between two adjacent lower electrodes is defined as L1, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1, and the thickness of the second region of the funnel-shaped groove in the first direction is H2.

[0139] In this embodiment of the invention, it is sufficient to ensure that L1 > L2 and H1 > H2.

[0140] The following example illustrates the process under different process parameters:

[0141] Example 1:

[0142] In IBE etching, the ion beam angle is 45°, the ion energy is 200V, the ion acceleration bias voltage is 200V, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas selected is argon, and the etching is carried out to the junction of the substrate and the lower electrode.

[0143] During RIE etching, the source electrode power is 200W, the bias electrode power is 100W, the etching chamber pressure is 10mT, the gas flow rate is 200sccm, the gas is argon, and the etching reaches 30nm on the substrate.

[0144] refer to Figure 19 , Figure 19 This is another structural schematic diagram corresponding to the completion of the MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention. Under these process parameters, the width of the bottom of the funnel-shaped groove is L2A, the width between two adjacent lower electrodes is L1A, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1A, and the thickness of the second region of the funnel-shaped groove in the first direction is H2A.

[0145] After experimental testing and removal of metal contaminants, no metal contaminants were found on the sidewalls of the upper electrode and the MTJ layer.

[0146] Example 2:

[0147] In IBE etching, the ion beam angle is 45°, the ion energy is 200V, the ion acceleration bias voltage is 200V, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas selected is argon, and the etching is carried out to the junction of the substrate and the lower electrode.

[0148] During RIE etching, the source electrode power was 200W, the bias electrode power was 200W, the etching chamber pressure was 10mT, the gas flow rate was 200sccm, the gas was argon, and the etching was performed up to 30nm on the substrate.

[0149] refer to Figure 20 , Figure 20 This is another structural schematic diagram corresponding to the completion of the MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention. Under these process parameters, the width of the bottom of the funnel-shaped groove is L2B, the width between two adjacent lower electrodes is L1B, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1B, and the thickness of the second region of the funnel-shaped groove in the first direction is H2B.

[0150] and Figure 19 Compared to the structures shown, L1B = L1A; L2B = L2A; H1B = H1A; H2B < H2A.

[0151] In other words, compared to the structure shown in Example 1, the position of the protruding structure at the junction of the first and second regions in the funnel-shaped trench is lowered, which weakens the shielding effect on the metal contamination sputtering path.

[0152] After experimental testing and cleaning of the metal contaminants, there were metal contaminants on the sidewall of the upper electrode, but no metal contaminants on the sidewall of the MTJ layer.

[0153] Example 3:

[0154] In IBE etching, the ion beam angle is 35°, the ion energy is 200V, the ion acceleration bias voltage is 200V, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas is argon, and the etching is carried out to the junction of the substrate and the lower electrode.

[0155] During RIE etching, the source electrode power was 200W, the bias electrode power was 200W, the etching chamber pressure was 10mT, the gas flow rate was 200sccm, the gas was argon, and the etching was performed up to 30nm on the substrate.

[0156] refer to Figure 21 , Figure 21This is another structural schematic diagram corresponding to the completion of the MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention. Under these process parameters, the width of the bottom of the funnel-shaped groove is L2C, the width between two adjacent lower electrodes is L1C, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1C, and the thickness of the second region of the funnel-shaped groove in the first direction is H2C.

[0157] and Figure 20 Compared to the structures shown, L1B = L1C; L2C < L2B; H1B = H1C; H2B = H2C.

[0158] In other words, compared to the structure shown in Example 2, the bottom width of the funnel-shaped groove is increased, further weakening the shielding effect on the metal contamination sputtering path.

[0159] After experimental testing, after the metal contamination was removed, there was still metal contamination on the upper electrode sidewall and the upper part of the MTJ layer sidewall. However, the metal contamination on the MTJ layer sidewall did not completely connect the upper and lower electrodes, and the device did not fail.

[0160] Example 4:

[0161] In IBE etching, the ion beam angle is 45°, the ion energy is 200V, the ion acceleration bias voltage is 200V, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas selected is argon, and the etching is carried out to the junction of the substrate and the lower electrode.

[0162] During RIE etching, the source electrode power was 600W, the bias electrode power was 600W, the etching chamber pressure was 10mT, the gas flow rate was 200sccm, the gas was argon, and the etching was performed up to 30nm on the substrate.

[0163] refer to Figure 22 , Figure 22 This is another structural schematic diagram corresponding to the completion of the MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention. Under these process parameters, the width of the bottom of the funnel-shaped groove is L2D, the width between two adjacent lower electrodes is L1D, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1D, and the thickness of the second region of the funnel-shaped groove in the first direction is H2D.

[0164] and Figure 20 Compared to the structures shown, L1D = L1B; L2D = L2B; H1D = H1B; H2D < H2B.

[0165] In other words, compared to the structure shown in Example 2, the position of the protruding structure at the junction of the first and second regions in the funnel-shaped groove is lowered, further weakening the shielding effect on the metal contamination sputtering path.

[0166] After experimental testing, after the metal contamination was removed, there was still metal contamination on the upper electrode sidewall and the upper part of the MTJ layer sidewall. However, the metal contamination on the MTJ layer sidewall did not completely connect the upper and lower electrodes, and the device did not fail.

[0167] Example 5:

[0168] In IBE etching, the ion beam angle is 45°, the ion energy is 200V, the ion acceleration bias voltage is 200V, the etching chamber pressure is 2mT, the gas flow rate is 100sccm, the gas selected is argon, and the etching is carried out to the junction of the substrate and the lower electrode.

[0169] During RIE etching, the source electrode power was 200W, the bias electrode power was 200W, the etching chamber pressure was 10mT, the gas flow rate was 200sccm, the gas was argon, and the etching was performed to a depth of 15nm on the substrate.

[0170] refer to Figure 23 , Figure 23 This is another structural schematic diagram corresponding to the completion of the MRAM magnetic tunnel sidewall contamination control method provided in this embodiment of the invention. Under these process parameters, the width of the bottom of the funnel-shaped groove is L2E, the width between two adjacent lower electrodes is L1E, the total thickness of the first and second regions of the funnel-shaped groove in the first direction is H1E, and the thickness of the second region of the funnel-shaped groove in the first direction is H2E.

[0171] and Figure 20 Compared to the structures shown, L1E = L1B; L2E = L2B; H1E < H1B; H2E < H2B.

[0172] In other words, compared to the structure shown in Example 2, the funnel-shaped trench is shallower and has a weaker ability to clean contaminants within the trench. Therefore, the metal contaminants within the trench will not transfer excessively to the sidewalls of the MRAM structure.

[0173] After experimental testing and removal of metal contaminants, there was no metal contamination on the upper electrode sidewall and the MTJ layer sidewall, but metal contamination residue remained in the trench, and the device did not fail.

[0174] Optionally, another embodiment of the present invention provides a method for controlling contamination of the sidewalls of MRAM magnetic tunnels, the method comprising:

[0175] A basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode;

[0176] The first etching process is performed on the surface of the upper electrode facing away from the substrate until the lower electrode is exposed. The size of a portion of the MTJ layer adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the MTJ layer remains unchanged in the first direction.

[0177] The second etching process is continued to make the size of all regions of the MTJ layer equal in the first direction, and the substrate and the lower electrode have funnel-shaped trenches, wherein the funnel-shaped trenches include a first region of the lower electrode and a second region of the substrate, the size of the first region gradually increases in the first direction, and the size of the second region remains unchanged in the first direction;

[0178] Remove metal contaminants from the bottom of the funnel-shaped groove.

[0179] In this embodiment, reference Figure 24 , Figure 24 A schematic diagram of a corresponding structure after the completion of another method for controlling contamination of the sidewall of a magnetic tunnel provided in this embodiment of the invention, as shown below. Figure 24 The structure shown also effectively prevents excessive metal contamination from adhering to the sidewalls of the MTJ layer.

[0180] It should be noted that the descriptions of unchanged dimensions in a certain direction in this application are all idealized descriptions. In the current actual etching process, it is impossible to achieve unchanged dimensions in a certain direction. The final actual product should be based on the product produced by the actual process.

[0181] It should be noted that the substrate in the embodiments of the present invention can be a dielectric layer of various materials, and therefore is also illustrated as "substrate / dielectric" in the accompanying drawings. The specific material is not limited in the embodiments of the present invention.

[0182] The present invention provides a detailed description of a method for controlling contamination on the sidewall of an MRAM magnetic tunnel. Specific examples have been used to illustrate the principle and implementation of the invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the invention. At the same time, those skilled in the art will know that there will be changes in the specific implementation and application scope based on the idea of ​​the invention. Therefore, the content of this specification should not be construed as a limitation of the invention.

[0183] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0184] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that elements inherent to a process, method, article, or apparatus that comprises a list of elements, or elements inherent to such processes, methods, articles, or apparatus, are also included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0185] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling contamination of the sidewalls of an MRAM magnetic tunnel, characterized in that, The control method includes: A basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode; The first etching process is performed on the surface of the upper electrode facing away from the substrate until the substrate is exposed, and the size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction. The second etching process is continued to make the dimensions of all regions of the lower electrode equal in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the dimensions of the first region gradually increase in the first direction, and the dimensions of the second region remain unchanged in the first direction; Remove metal contaminants from the bottom of the funnel-shaped groove.

2. The control method according to claim 1, characterized in that, The distance between the surface of the MTJ layer facing away from the upper electrode and the surface of the first region facing away from the second region is Hs; The thickness of the lower electrode in the first direction is G1; Where Hs > G1, or Hs = G1.

3. The control method according to claim 1, characterized in that, The first etching process includes: The upper electrode is first etched from the surface away from the substrate using plasma beam etching until the substrate is exposed. The size of a portion of the lower electrode adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the lower electrode remains unchanged in the first direction.

4. The control method according to claim 3, characterized in that, In the plasma beam etching method, the ion energy is 50V-600V; Ion acceleration bias voltage is 50V-1000V; The gas flow rate is 10 sccm-500 sccm.

5. The control method according to claim 3, characterized in that, In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

6. The control method according to claim 3, characterized in that, Before the first etching process, the control method further includes: A mask layer is provided on the surface of the upper electrode facing away from the substrate, and the mask layer includes a plurality of mask units.

7. The control method according to claim 6, characterized in that, The distance between two adjacent mask units is X; the thickness of each mask unit in the first direction is Y3; the total thickness of the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y2; The total thickness of the mask unit, the lower electrode, the MTJ layer, and the upper electrode in the first direction is Y1, where Y1 = Y2 + Y3; Define the first angle Second angle The third angle is A3, where 0 < A3 - A2 ≤ 5°; In the plasma beam etching method described above The incident angle of the ion beam is greater than A1 and less than A3.

8. The control method according to claim 3, characterized in that, The second etching process includes: A second etching process is performed using reactive ion etching to ensure that at least all regions of the lower electrode have equal dimensions in the first direction, and the substrate has a funnel-shaped trench, wherein the funnel-shaped trench includes a first region away from the bottom surface of the substrate and a second region adjacent to the bottom surface of the substrate, the first region gradually increases in size in the first direction, and the second region remains unchanged in size in the first direction.

9. The control method according to claim 8, characterized in that, The DC bias voltage in the reactive ion etching method is less than or equal to the ion energy in the plasma beam etching method.

10. The control method according to claim 8, characterized in that, In the reactive ion etching method, the selectivity ratio of etching medium to etching metal is greater than 1.

5.

11. The control method according to claim 8, characterized in that, In the reactive ion etching method, the etching thickness of the substrate is greater than 10 nm.

12. The control method according to claim 8, characterized in that, In the reactive ion etching method, the source electrode power is 100W-1000W; The bias electrode power is 100W-1500W; The etching chamber pressure is 2mT-20mT; The gas flow rate is 10 sccm-500 sccm.

13. The control method according to claim 8, characterized in that, In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas, or different combinations of the above gases.

14. A method for controlling contamination of the sidewall of an MRAM magnetic tunnel, characterized in that, The control method includes: A basic structure is provided, the basic structure including a substrate, a lower electrode, an MTJ layer and an upper electrode arranged sequentially in a first direction, the first direction being perpendicular to the substrate and pointing from the substrate to the lower electrode; The first etching process is performed on the surface of the upper electrode facing away from the substrate until the lower electrode is exposed. The size of a portion of the MTJ layer adjacent to the substrate gradually decreases in the first direction, while the size of the remaining portion of the MTJ layer remains unchanged in the first direction. The second etching process is continued to make the size of all regions of the MTJ layer equal in the first direction, and the substrate and the lower electrode have funnel-shaped trenches, wherein the funnel-shaped trenches include a first region of the lower electrode and a second region of the substrate, the size of the first region gradually increases in the first direction, and the size of the second region remains unchanged in the first direction; Remove metal contaminants from the bottom of the funnel-shaped groove.

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